H3C S7500E Series Ethernet Switches Operation Manual

Operation Manual – DHCP
H3C S7500E Series Ethernet Switches Chapter 5 DHCP Snooping Configuration
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 Note:
z To support Option 82, it is required to perform related configuration on both the
DHCP server and the device enabled with DHCP Snooping. Refer to
Configuring
the Handling Mode for Option 82
for DHCP server configuration of this kind.
z If the handling strategy of the DHCP-Snooping-enabled device is configured as
replace, you need to configure a padding format for Option 82. If the handling
strategy is keep or drop, you need not configure any padding format.
z If the Option 82 is padded with the device name (sysname) of a node, the device
name must contain no spaces. Otherwise, the DHCP-Snooping-enabled device will
drop the message.
5.4 Displaying and Maintaining DHCP Snooping
To do… Use the command… Remarks
Display DHCP snooping
address binding information
display dhcp-snooping
Display information about
trusted ports
display dhcp-snooping
trust
Available in any
view
Clear DHCP snooping
address binding information
reset dhcp-snooping { all |
ip ip-address }
Available in user
view
5.5 DHCP Snooping Configuration Example
I. Network requirements
z Switch B is connected to a DHCP server through GigabitEthernet 2/0/1, and to two
DHCP clients through GigabitEthernet 2/0/2 and GigabitEthernet 2/0/3.
z GigabitEthernet 2/0/1 forwards DHCP server responses while the other two do
not.
z Switch B records clients’ IP-to-MAC address bindings in DHCP-REQUEST
messages and DHCP-ACK messages received from trusted ports.
z Switch B supports Option 82. After receiving a DHCP request from the client,
Switch B adds Option 82 padded in verbose format to the request message and
forwards the message to the DHCP server.